In the electronics industry, the tendency has been to reduce the size of electronic devices such as camcorders and portable telephones while increasing performance and speed. Integrated circuit packages for complex systems typically are comprised of multiple interconnected integrated circuit chips. The integrated circuit chips usually are made from a semiconductor material such as silicon or gallium arsenide. The integrated circuit chips may be mounted in packages that are then mounted on printed wiring boards.
Packages including integrated circuit chips typically have numerous external pins that are mechanically attached by solder or a variety of other known techniques to conductor patterns on the printed wiring board. Solder joint reliability is an important factor for achieving good quality semiconductor packaging.
Typically, the packages on which these integrated semiconductor chips are mounted include a substrate or other chip-mounting device. One example of such a substrate is a leadframe. Leadframes also typically include at least an area on which an integrated circuit chip is mounted and multiple power, ground, and/or signal leads to which power, ground, and/or signal sites of the integrated semiconductor chip are electronically attached. Semiconductor integrated chips may be attached to the leadframe using adhesive or any other techniques for attaching such chips to a leadframe which are commonly known to those skilled in the art, such as soldering. The power, ground and signal sites on the chip may then be electrically connected to individual leads of the leadframe.
Leadframes have been used extensively in the integrated circuit packaging industry mainly because of their low manufacturing cost and high reliability. Leadframe packages remain a cost-effective solution for packaging integrated circuits.
Typical leadframe packages include a die attach paddle, or pad, surrounded by a number of leads. The leads are attached to the die pad. An integrated circuit chip is attached to the die pad. After the die is attached to the die pad, a wire-bonding process is used to make electrical interconnections between the integrated circuit and the leads of the leadframe.
One problem that persists with these conventional leadframes is that the leadframe's pre-arranged leads surrounding the die pad occupy a large mounting area which is limiting the output of the number of dies per leadframe after singulation. The modern trend of semiconductor device miniaturization requires that the mounting area of the semiconductor package is minimized. Also, the conventional leadframes have thick package profile which is detrimental to achieving device miniaturization.
Furthermore, separation of the leads from the leadframe so as to electrically insulate each contact from each other is complex and cumbersome.
After wire bonding, the leadframe with the integrated circuit attached is encapsulated using a mold compound. Such enclosures may include encapsulant in a plastic or a multi-part housing made of plastic ceramic, or metal. The enclosure protects the leadframe and the attached chip from physical, electrical, and/or chemical damage. Finally, post mold curing and singulation steps are conducted to complete the packaging process.
Sometimes passive devices are added to the semiconductor package, typically attached between two leads, before the encapsulation. Good flowability of the mold compound under such passive devices is important for ensuring good encapsulation of the semiconductor package. However, the conventional leadframes have poor flowability of the mold compound under such passive devices.
The leadframe and attached chip(s) may be mounted on, for example, a circuit board, or card along with other leadframes or devices. The circuit board or card may then be incorporated into a wide variety of devices such as computers, automobiles, and appliances, among others.
As integrated circuits have become smaller with increased performance capabilities, new leadframes and new processes of wire-bonding, soldering, and mounting for integrated circuits have been adapted to accommodate these integrated circuits.
Leadless leadframe has been proposed to counter some of the problems of the conventional leadframes. However, under the current status of the art, problems still exist concerning the thickness of the package profile, the solder joint reliability, and the mold compound flowability under discrete passive components when such components are added to the package, etc.
Thus, a need still remains for reducing the package thickness, improving the solder joint reliability, and improving the mold compound flowability under discrete passive components. In view of the ever-increasing commercial competitive pressures, along with growing consumer expectations and the diminishing opportunities for meaningful product differentiation in the marketplace, it is critical that answers be found for these problems. Additionally, the need to reduce costs, improve efficiencies and performance, and meet competitive pressures, adds an even greater urgency to the critical necessity for finding answers to these problems.
Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.